#include <stdio.h> 
#include <sys/types.h> 
#include <unistd.h> 
int main () 
{ 
  pid_t child_pid; 

  printf ("the main program process ID is %d\n", 
           (int) getpid ()); 
  child_pid = fork (); 
  if (child_pid != 0) { 
    printf ("this is the parent process, with id %d\n", 
            (int) getpid ()); 
    printf ("the child's process ID is %d\n", (int) child_pid); 
  } 
  else 
    printf ("this is the child process, with id %d\n", 
             (int)getpid ()); 

  return 0; 
} 
